This was, in actuality, a blind spot of Steiner's seeing the presence of evil and connecting it to beings in a higher plane of existence, but was only seeing the dark spirits in the lower astral plane and was reading their energy correctly, that they are malevolent and quite savage beings, but he did not realize that there were dark extraterrestrial lost soul spirits intermixing and actually controlling the dark fallen angelic spirit meddlers that are abundant in the lower astral plane. They are the source of evil because the spirit meddlers were the first to fall from grace and lose their standing and place in heaven, so to speak, by choosing the temptation to serve the ego more and more, and were unable to recover their former lofty status when they became self-corrupted in their thinking. That is a cautionary tale for everyone in what can happen in neglecting spiritual development and perspective about what is truly most important. So he was unaware of extraterrestrials per se, and that is simply because the idea did not occur to him that it was possible. This is a closely guarded secret of the extraterrestrials themselves. They don't want you to know this and have worked avidly to program the minds of everyone that advanced extraterrestrial life is only a theoretical possibility, and perhaps an unlikely one and, in any event, the Earth is a tiny planet, in a tiny solar system, on the edge of a galaxy, and so far from the nearest star, being visited by other sentient beings would be impossible. That is all untrue, of course, but this is what science says because the extraterrestrials want science to tell you that. So this is not a fault of Steiner's but simply that he was working within the culture of the day, and so there were many things carved in stone within the beliefs of everyone as happens today as well. This is why creative thinkers are few and far between, because it is not a question of becoming better at being a human but actually recovering from severe deprivations to limit ability to think beyond the conventional.